Open hearth furnace



Oct 17, 1939. 'w. RT I 2,176,270

OPEN HEARTH FURNACE A Filed Dec. 17, 1937 5 Sheets-Sheet l A TTORNEYS.

Oct 17, 1939. w. AfMORTCN OPEN HEARTH FURNACE 3 Sheets-Sheet 3 FiledDec. 17, 1957 I N V EN TOR.

A TTORNEYS.

meme a. 11, 1939 ammo UNITED STATES PATENT orrlcr:

' ammo V OPEN HEART]! macs notation of Penny I Application December 17,19:1, Serial-No. 180,34:

4 Claims.

This invention relates to new and useful improvements in open hearthfurnaces, more particularly in the method of flrings'uch' furnaces andautomatically controlling the combustion system, and it is among theobjects thereof to provide a furnace structure which shall be adaptedfor mechanically controlled continuous flring as distinguished from thereversing regenerative type furnaces, and in which the application of aheating ilame is such as will provide regul'able temperatureslongitudinally and'transversely of the melting hearth and chamber.

Another object of the invention is the provision of means for directingan adjustable heating flame into the furnace, and s0 removing the wasteproducts therefrom that the atmosphere into which the fuel is directedwill be free'of any excess of waste gases to thereby insure maximumthermal em.- clency.

A further object of theinvention is the provision of means forcontrolling the fuel supply and stack draft in response to variations inpressure of the furnace atmosphere. I

The reversing type furnace is not well adapted to a modern combustioncontrol system. The burner is alternately a burner and a waste gasoutlet and with such an arrangement the problem of properly burning thefuel at correct velocities is serious. In this new furnace. a pair ofburner ports are provided having an area much smaller than the totalarea of the two outlets, resulting in better combustion, flame directionand control.

These and other objects of the. invention will become more apparent froma consideration of the accompanying drawings constituting a part hereofin which like reference characters designate like parts and in which:

, Fig. l is a horizontal section of an open hearth furnace talren alongthe line ll, Fig. 4;

Fig. 2 ahorlzontal section of one-half of the openhearth furnace takenalong the :line 2-2, as Fig.6;

A further object of the invention is to conduct Fig. 3 a verticalsection taken along the line 3-4, Fig. 2;

Fig. 4 a vertical section taken along the line 4-4, Fig. 6; 1

Fig. 5 a plan view of the complete furnace B viewed from the topof Fig.6;.

Fig. 6 a vertical cross-section longitudinally of the furnace takenalong the line 8-8, Fig. 2;

Fig. 7 a plan view of the open hearth f 3% diagrammaticallyillustratingmeans for controlto ling the stack draft in response to pressureerential in the furnacechamber; and

Fig. 8 a diagatic view partially in section of the stack draft controlmeans of Fig. 7.

With reference to the several figures of the 515 drawings, numeral 6designates the roof, 2 the hearth, and 3 and 8 the sidewalls of thefurnace. The hearth 2 is provided with a lining it of dolomite or thelike which isrenewedfor each charge. Both the roof and hearth are convegat their go ends as shown in Fig. 6, forming a constricted areaconstituting firing ports ii and waste gas exit passages l, the firingports extending into preheated air passages 3 and the waste gas exitports l communicating with waste gas passages El surroung 5 7 thepreheated air passages t. Dampers to. may he provided to distribute theflow oi waste gases around the preheat air passage 8.

Firing ports (-3 are slightly oiic'set from the longitudinal ends of thefurnace, and the hea so flame extends from the mouth of the firing portlongitudinally of the furnace, and the products of combustion pass in aloop toward and into the waste gas passages l. Burner pipes ill extendinto the firing ports t, these being movable longitudig5 nally by meansof a motor drive mechanism generally designated by the numeral it forthe purpose hereinafter explained, the burner pipes Bil being at aslight inclination to impinge the heating flame downward against thesurface or the charge 49 on the furnace hearth.

The'preheeted air and waste gas passages 8 and 9, respectively, extendvertically downward from the furnace to the recuperator structures,generally designated by the reference numeral 62, and which consist ofrefractory tile l3, forming vertical waste gas passages and horizontalair passages through which the products of combustion from the furnaceand the preheated air delivered to the furnace, respectively pass. Pokeholes provided 50 with refractory plugs it extend through the roof ofthe recuperators to render the vertical waste gas passages accessiblefor cleaning;

As shown. in Fig. e, the waste gases pass down- 'wardly from the exhaustport l around the veris tical preheated air passage 8 in heat exchangerelation therewith, into a slag pocket l6, from which slag is removedthrough a door II. The waste gases pass vertically upward into thecollecting chamber above the recuperator tile. thence downwardly throughthe vertical passages to a common chamber at the bottom of the tile-fromthe waste gases directly to the stack passage l8, if

desired, thereby regulating the degree of preheat of the recuperator,and for the removal of surplus waste gases. from mixed fuels containingblast furnace gas, to avoid high temperature differentials in the baseof the recuperator; and further to compensate for resistance to thewaste gas flue in the recuperator toward the end of a campaign when anexcess of solids may accumulate in the waste gas flues of therecuperator.

The passages iii are also provided with dampers 22 whereby the amount ofgases drawn through the respective recuperators may be regulatecl.

The air to be preheated is conducted into the lower horizontal passage23 of the recuperator tile structure, Figs. 4 and 5, there being aplurality of inlet passages from a manifold 24, which is provided with ablower 25 to supply the air to the recuperator structure in any desiredregulable quantities.

The operation of the above-described open hearth furnace is briefly asfollows: When the material is charged in the chamber, it is piled on thelining 5 of the hearth 2 and the burners are lighted and adjusted todeliver a desired amount of heating medium'through the burner port 6.The products of combustion are directed against the material on thehearth and then pass to the waste gas exits I and downwardly through thevertical passage 9 surrounding the preheated air passage 8 to therecuperator-structure. Because of the continuous removal of the productsof combustion through the ports I, combustion will take place in anatmosphere continuously cleared of products of combustion. During theinitial stages .of firing, it is desirable to retract th burner pipesill from the firing ports to obtain increased ignition rates byutilizing the stored heat of the refractory walls of the firing ports asan aid to efficient combustion. The burners are then gradually moved toan advanced position at a predetermined rate in the firing port 6 tovary the flame length and extend the area subjected to the products ofcombustion, as shown in Fig. 6 of the drawings. This movement of theburner pipes is effected by the drive mechanism II which may be operatedby a reversing motor through a gear reduction mechanism as shown.

The drive mechanism is designed to gradually move the burner'into theport to change the flame length and concentration of heat during theprogress of a melting cycle; thus, for example, when a cold charge isplaced in the furnace, it will occupy a substantial portion of the spacebetween the hearth and roof, and it is diflicult to burn a long flame athigh temperatures uniformly in the cold furnace at the start of theheat. By properly positioning the burner at the beginning of the heat,the flame is concentrated on the charge adjacent the burner port andmelting progressively is advanced toward the center of the hearth. Whenthe burner is drawn back into the burner port, the' mixing of the fueland air takes place in a confined area and as it progresses into thefurnace the heat flame islengthened so that the hotter portion of theflame extends into the charge remote from the burner port. The fuelsupply may be gradually diminished as the "melting progresses so that asthe flame is lengthened the firing rate or thermal input per unit oftime is reduced to obtain the most effective distribution of the fuel tothe bath.

Because of the unidirectional continuous firing from both ends of, thefurnace, it is desirable to maintain balanced pressures at the exhaustports, which can be accomplished by pressure recording mechanism that isstandard equipment and which is' located in the exhaust passages andwhich, through suitable control mechanism, automatically regulates thestack dampers to maintain a balanced pressure.

It is evident from the foregoing description of the invention that openhearth furnaces constructed in accordance therewith are adapted'to themelting and refining of steel in an economical and emcient manner,whereby the time of melting is reduced, thereby increasing theproduction capacity of the furnace.

It is also apparent that by means of the arrangement of waste gaspassage and preheat air passage in heat exchange relation in the travelof the air and gases between the furnace and recuperator structures, amuch higher preheat for the air is obtainable, and by regulating boththe application of heat and the heat intensity from 4 the firing portend toward the center of the furnace, the materials can be melted at afaster rate without creating waste heat in the furnace.

With reference to Figs. 7 and 8 of the drawings, the internal pressureof the furnace chamber is regulated by means of the following mechinder33, the piston of which actuates the stack damper 34, a manuallyoperated valve 35 being interposed in conduits 3| and 32.

It is desirable during the heating period of the furnace to maintainpredetermined pressure in the furnace chamber, this being automaticallyaccomplished by the regulator diaphragm 28 which, by being exposed toboth the pressure within the furnace chamber through conduit 26 and theatmosphere through conduit 21, will operate valve 30 in response tovariation in the pressure differentials it is desired to maintain.

When the fuel and air supply to the furnace have been reduced after thecharge in the furnace has been brought to a molten stage, the pressuredecreases in the stack and the furnace pressure drops accordingly. Bymeans of the control mechanism of Fig. 8 the stack draft dampers 34 areautomatically adjusted to compensate for the lesser volume of theproducts of combustion so that the some pressure may be maintained inthe furnace,'which is especially desirable where prolonged metallurgicalprocessing is necessary as apparent to those skilled in the art thatvarious modifications may be made in the details of construction withoutdeparting from the principles herein ,set forth. I claim:

1. In an open hearth furnace, a hearth, roof and side walls forming \amelting chambenfiring ports at opposite ends of said chamber and wastegas exit ports adjacent the firing ports, burners extending into thefiring ports, preheat air passages of substantial length communicatingwith said firingp'orts. waste gas passages surrounding said airpassages, a recuperator tile structure communicating with said preheatand waste gas passages, means for directing. regulable quantities offuel and preheated air to said firing ports, and means to simultaneouslyand continuously withdraw the products of combustion through the wastegas exit adJacent said 20 ports whereby the melting-flame is extendedinto the continuously clearing atmosphere of the fur- 2. In an openhearth furnace, a hearth, roof and side wall structures comprising amelting chamber, firing ports at the respective ends of 1 said chamber,a preheated air passage extending vertically from said firing ports torecuperator structures, waste gas exit ports adjacent the firing portshaving a passage coextensive with the preheated air passage andcompletely surrounding the latter, a recuperator tile structurecommunicating with said preheat and waste gas es,

means for distributing the fiow of the waste gases aroimd the preheatedair passage and burners extending into said firing ports.

3. In an open hearth furnace, a hearth, roof and side wall structurescomprising a melting chamber, firing ports at the respective ends ofsaid chamber, a preheated air passageextending vertically from saidfiring'ports to recuperator structures, waste gas exit ports adjacentthe firing ports having a passage coextensive with the preheated airpassage and completely surround- .ing the latter, a recuperator tilestructure communicating with said preheat and waste gas passages, andmeans for regulating the volume and heat intensity of the preheated airentering the furnace chamber.

4. Inan open hearth furnace, a hearth, roof and side wall structurescomprising a melting chamber, firing ports at the respective ends ofsaid chamber, a preheated air passage extending vertically from saidfiring ports to recuperator structures, waste gas exit ports arflacentthe firing ports having a passage coextensive with the preheated airpassage, a recuperator tile structure communicating with said preheatand waste gas passages, means for regulating the rate of exhaust of thewaste gases from the melting chamber through the respective recuperator

